Question

A 2 year old male child has symptoms that include fatigue, nausea, voimiting and diarrhea. These symptoms have persisted for several days. Stool cultures for bacteria pathogens such as Salmonella and Shigella were negative. The stool was also checked for ova and parasites, and the results were negative. The day-care center that the child attends has had a previous problem with contaminated water and the physician is suspicous that this infections might be caused by Cryptosporidium, a waterborne pathogen. However, because no parasties were found, he is not certain how to proceed. Does a negative finding rule out the presence of a parasite? What other type of testing could be done? How does the sensitivity of testing such as enzyme immunoassay compare with visual inspection of stained slides? What are other advantages of enzyme immunoassay tests?

Answer 1

A. Does a negative finding rule out the presence of a parasite?
No, some error and sensitive and specificity of test play a role
B. What other type of testing could be done?

Detection of Cryptosporidiumcan be difficult,
1. submition of several stool samples over several days.
stool specimens are examined
A. acid-fast staining
B. direct fluorescent antibody [DFA]
C. enzyme immunoassays for detection of Cryptosporidium sp. antigens).

D. Molecular methods like polymerase chain reaction – PCR)

3. How does the sensitivity of testing such as enzyme immunoassay compare with visual inspection of stained slides?

diagnostic sensitivities of Cryptosporidium by enzyme immunoassays(EIA) coupled with confirmation of positive reactions were 91.4–93.4 %,
The sensitivity of auramine phenol microscopy was 92% that of immunofluorescence microscopy (IFM) was 97.4 %,
4. What are other advantages of enzyme immunoassay tests?
study concluded that stool microscopic Modified acid fast staining is more sensitive method than ELISA for detection of Cryptosporidium in stool samples
but
the specificity of ELISA was more than microscopy.